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Uniformity, specificity and variability of corticocortical connectivity
1Department of Psychology, University of Newcastle upon Tyne, UK. claush@bu.edu
Summary
Quantitative analysis of cat visual cortex connectivity reveals four distinct subdivisions within the middle suprasylvian sulcus (MSS). Connection strengths vary greatly between animals, challenging subjective classifications and highlighting area size as a key factor in connection strength.
Area of Science:
- Neuroscience
- Comparative Anatomy
- Systems Neuroscience
Background:
- Subjective assessments of cortical connectivity are common in mammalian brain studies.
- Previous methods relied on qualitative descriptions of connection patterns and strengths.
- Objective, quantitative analysis of corticocortical connections is needed for a deeper understanding of brain networks.
Purpose of the Study:
- To apply statistical analyses to quantitative corticocortical connection data in the cat visual cortex.
- To determine if connection strengths exhibit inherent clustering or if classifications are imposed.
- To identify distinct subdivisions within the middle suprasylvian sulcus (MSS) based on connection patterns.
Main Methods:
- Injections of WGA-HRP tracer into visual areas of 11 adult cats.
- Counting retrogradely labeled cells in coronal sections of the visual cortex.
- Non-parametric cluster analyses, Monte Carlo simulations, and linear regression to evaluate connection strengths and area size relationships.
Main Results:
- Cortical area size was uniform, but connection strengths between areas were highly variable across individual animals.
- Connection strength distribution was continuous and monotonic, with most connections being absent or very low density.
- Identified four connectionally distinct subdivisions within the MSS: areas 21a, PMLS, AMLS (medial bank), and PLLS (lateral bank).
Conclusions:
- Subjective classifications of connection strengths (e.g., weak, strong) impose structure not inherent in the data.
- Despite variability, similarities in connection strength profiles allowed for the identification of distinct MSS subdivisions.
- Connection strength is positively correlated with cortical area size on average, though this relationship varies between medial and lateral bank areas.